1. Field of the Invention
This invention relates generally to the field of cards, labels or other planar and laminar structures containing embedded devices interactive with external readers such as electronic access control or identification card readers, and more particularly concerns a method of continuously manufacturing such cards, labels and structures.
2. State of the Prior Art
The use of plastic cards as carriers for embedded electronic, magnetic or other interactive devices has grown and continues to grow at a rapid pace. Early key cards contained magnetic coding elements such as barium ferrite and Wiegand wire elements, and such cards are still in widespread use. These cards are inserted into a card reader unit equipped with appropriate sensors which, upon detecting a correct card coding pattern, grant access to protected premises or equipment to the card holder. Advances in solid state electronics and large scale integrated circuit design have produced relatively complex microcircuits or chips suitable for encapsulation in thin card structures. These chips have greatly increased the capabilities of the cards. One area of improvement has been the incorporation of programmable data storage and data processing in the card, leading to so called smart cards used, for example, as refillable cash cards for consumer purchases. Another area of improvement is the development of radio frequency communication between the card and the card reader, resulting in so called non-contact or proximity cards. A principal application of this technology is in radio frequency identification (RFID) proximity cards which incorporate radio frequency transponder integrated circuits or chips. By combining these two technologies non-contact smart cards have been developed more recently. Furthermore, these technologies are not limited to access control or financial transaction cards. Other uses include interactive labels on shipping or storage crates, pallets and other containers to automate and speed-up routing and processing of goods in transit and inventory control of stored goods. Such labels may be plastic sheet structures containing RFID transponder tag integrated circuit chips which cooperate with proximity tag readers. The labels may be programmable with data such as container content, dates, destination, etc. Other uses for such interactive cards and labels are still being found, so that this invention is directed broadly to laminar assemblies with embedded interactive elements, without limitation to any particular use or application of the laminar assembly.
A great deal of effort and innovation has been directed to the problem of economically manufacturing such plastic carrier cards. The large volume, low cost manufacture of carrier cards with embedded electronic elements is more difficult than may appear at first thought. Standardization of the carrier cards has resulted in tight dimensional tolerances including card thickness. There is also increasing demand for ever thinner cards, approaching the thickness of magnetic stripe credit cards, while still containing the embedded interactive electronics including in some cases microprocessor chips. Along with the dimensional requirements is a demand for high quality appearance and finish of these cards. The ability to deliver a choice of surface texture and full color graphics on the card is necessary for competitive participation in this market. Company logos and user information including photographic identification may be applied to the card.
One common approach has been to use a core sheet of sufficient thickness in which are cut openings for receiving the electronic components. The core is laminated between top and bottom layers to enclose these components. Onto this assembly may be applied sheets with pre-printed graphics, and these are in turn covered with protective layers which guard the graphics against wear during handling of the card. The openings in the core sheet are filled to hold the components in place and minimize surface irregularities in the finished card. Various processes are available for this purpose including wet chemistry processes, ultraviolet cured epoxy fillers, self curing fillers, heat cured filler materials, and air cured epoxies among other techniques. These conventional approaches involve many intermediate steps in the manufacture of the cards and require relatively costly and difficult to handle raw materials including very thin plastic sheets of closely controlled thickness. Efforts to simplify card manufacture have been directed to injection molding of carrier cards. Although this method can yield high quality cards it calls for expensive injection molds and production volume is limited by the number of cavities in the molds.
U.S. Pat. No. 5,817,207 to Leighton discloses a hot lamination method whereby a micro-circuit is encapsulated between two discrete sheets of plastic under heat and pressure so that the plastic flows around the electronic device. While in principle this method eliminates the need for a separate core sheet with cut out openings for receiving the microcircuit, it is a very difficult process to carry out in practice and still requires considerable handling and cutting of plastic sheets and loading these into the lamination press one at a time.
In spite of the rapid growth in usage of interactive cards and labels, existing technology for the economical manufacture of those items has failed to keep pace with demand. A continuing need exists for a lower cost method of high volume manufacture of laminar structures, such as cards and labels, with embedded interactive or other elements.